The present invention is related to a technique for generating signals (will be referred to as “pulse-width modulation signals” hereinafter), the pulse widths of which have been set in response to a time sequence of a plurality of data.
Signal generating apparatuses (PWM modulation circuits) which produce pulse-width modulation signals from time sequences of digital-formatted data are suitably utilized in, for example, class-D amplifying apparatuses. JP-A-2006-262261 has disclosed the following technical idea: That is, while sections during which the numeral values of the respective data exceed the carrier signals formed by count values generated from the counter circuit are defined as the pulse widths, the pulse-width modulation signals are generated. The carrier signals are such sawtooth signals, the amplitudes of which are increased, or decreased at the predetermined frequency.
However, in the arrangements disclosed in JP-A-2006-262261, the strengths of the signal components corresponding to the frequency of the carrier signals within the pulse-width modulation signals become conspicuous. As a result, there is such a problem of electro magnetic interference (EMI) caused by the above-described signal components. The present invention has been made by considering the above-described problem, and therefore, has an object to provide a technical idea capable of suppressing the electro magnetic interference caused by the pulse-width modulation.